Organic light emitting diode (OLED) display panel due to the advantages of thin, light, wide viewing angle, active light, light color continuously adjustable, low cost, fast response, low energy consumption, low drive voltage, wide operating temperature range, simple production process, high luminous efficiency and flexible display, etc., has been listed as a promising future generation of display technology. OLED display devices are usually use ITO pixel electrode and metal electrodes, as the device anode and cathode, respectively. By driven under a certain voltage, electron and hole transport layer migrate to the light-emitting layer, and meet in the light-emitting layer to issue visible light.
The OLED display device is divided into passive matrix type (PMOLED) and active matrix type (AMOLED) according to the driving method. AMOLED is a current driving device, when a current flow through the organic light-emitting diode, the brightness of the organic light-emitting diode is determined by the current flowing through its own, and the formula is: Ids=K(Vgs−Vth)x. Wherein Vth is the threshold voltage, k is the coefficient, and x is the power value in the drive current calculation formula. Most of the integrated circuits only transmit voltage signals, so AMOLED pixel drive circuit needs to complete the task turning voltage signal into the current signal, the traditional AMOLED pixel drive circuit for the 2T1C structure, that is, two thin film transistors plus a storage capacitor.
However, the threshold voltage and the coefficient of the driving thin film transistor between each pixel of the AMOLED are different, so that the driving current at the same driving voltage does not coincide, resulting in uneven luminance of AMOLED, which affects the display quality of AMOLED display device.